Computer hackers used sophisticated password-detection software in an attempt to swindle £229m ($317m) from one of Japan’s largest banking groups, a court heard on Wednesday.

In a plot seemingly cribbed from a Hollywood film, a “dishonest, bold” gang of cyber-crooks raided the City premises of Sumitomo Mitsui Banking at night to install “keylogger” programmes to record employees’ log-in details, prosecutors allege.

Assisted by an “inside man” who worked as a security supervisor at the bank, the thieves then attempted to make more than 20 electronic transfers involving multi-million pound sums from the accounts of big Sumitomo customers, including Nomura Asset Management and Toshiba, it is alleged.

The money was intended for accounts set up in locations such as Dubai and Singapore, but the men failed to realise that the keylogging software had inadvertently captured an error, jurors at Snaresbrook Crown Court in east London were told.

Several members of the gang, including two computer experts and the Sumitomo security guard, have pleaded guilty to conspiracy to steal.

The Crown is now pursuing three other people suspected of serving as “fronts” for the companies and bank accounts set up to receive the stolen funds in September and October 2004.

“The attempt was made by surreptitiously entering the bank at night, by corrupting its computer system and by attempting to electronically transfer money,” said prosecutor Simon Farrell, QC. “A number of people were involved in different ways to steal the money and some were closely connected to its distribution around the world.”

Hugh Rodley, David Nash and Inger Malmros deny the charges in what is expected to be a six-week trial. Bernard Davies, another defendant, died last weekend.

Jurors were told how the keylogger software could capture staff passwords and log-in details surreptitiously by taking frequent pictures of their computer screens. The fraudsters would then return to the bank to retrieve the screen shots and plug the information into electronic transfer requests.

“Fortunately for the bank, those transfers failed,” said Mr Farrell. Staff discovered the plot after realising their computers had been tampered with.